1. Field
The invention relates to a tool for securely holding gem stones to be contour ground, sanded and polished in cabochon style with a domed smooth surface.
2. Prior Art
Cabochon type gem stones have conventionally been held for grinding, sanding and polishing, by being adhered to a "dop" stick with wax, which is heated along with the stone to be adhered to the "dop" stick. Gemstones such as agate, jasper, petrified wood, turquoise, and others, are ground and polished with a contoured or domed top surface, and may be oval, round, square or of a freeform overall general outside shape. These domed type cuts are referred to as cabochons or cabs.
Gemstones are cut cabochon style to reveal the beauty of color and included mineral patterns in the stone. A diamond or other fully transparent precious type gemstone generally requires that flat facets be ground on all surfaces of the stone to reflect light from within the stone, and a stone so cut is termed a facet cut stone, instead of a cabochon cut stone.
Holding cabochon type stones on a "dop" stick with wax is a long practice but frequently unsatisfactory technique. During the grinding operation the grinding wheel and stone are showered with water to keep the gemstone from overheating and to flush away loosened grit from wheel and stone. The water often chills the wax, causing the wax to become brittle, break loose, allowing the stone to "pop-off" the stick. Very often the sanding of the stone is done on a motor driven belt or drum covered with dry sanding cloth. This generates heat in the gemstone which heat is transferred to the wax adhering it to the stick, causing the wax to become soft and allow the stone to shift position on the stick or slide from the stick. The polishing of cabochon gemstones is usually performed on a motor driven disc, drum or belt covered with felt or leather. The polishing operation is performed with water mixed with polishing powders applied to the buff. A minimum amount of moisture is used to attain the polish and it is an insufficient amount of moisture to cool the gemstone. As in the sanding operation the gemstone generates heat, softening the wax and allowing stone to shift or release from the stick.
Gem vises have been utilized for holding precious gem stones, particularly diamonds. Exemplary of gem vises are those described in the following patents:
The Lea Patent, U.S. Pat. No. 2,612,735, describes a hand-held vise for ovate stones wherein a thumb screw moves opposed jaws, which are an integral part of a U-shaped vise towards one another.
U.S. Pat. Nos. 2,270,420; 1,147,517; 605,193 are chuck-type holders which have extending fingers which are moved towards one another by circumferential pressure thereon near the base of the fingers within the chuck.
U.S. Pat. Nos. 2,394,242 and 2,390,175 illustrate a dop for holding diamonds, and is similar in construction and operation to the device described in the Lea Patent, i.e., the jaws are moved towards one another by a transverse screw. A similar structure involving one or two thumb screws to move one or both jaws of a vise is described in U.S. Pat. No. 631,562.
The diamond holder illustrated in U.S. Pat. No. 2,309,050 involves a pair of fixed jaws with a movable axial plunger which forces a gem between the jaws.